Deep submergence pressure compensator

ABSTRACT

A compensator for an underwater deep submergence fluid system wherein the compensator includes a cylinder and piston combination; one end of the cylinder being connected to the fluid system and the other end thereof opening to the ambient water environment; and the cylinder being pre-pressurized to a predetermined pressure so that the system components can be of minimum volume and construction.

United States Patent Hoffman Aug. 5, 1975 [5 DEEP SUBMERGENCE PRESSURE 3.611.975 10/1971 Ashbrook 114/235 B COMPENSATOR 3.626.881 12/1971 Lovinghamm. 1 14/16 E 3.665 833 5/1972 Sege 114/16 E [75] Inventor: Ro ert T- H ffm n, K il H ii 3,716,009 2/1973 Strickland 114 16 E [73] Assignee: The United States of America as I represented by the Secretary of the Primary 'y BIIX N W hi D C Assistant Examiner-Charles E. Frankfort Attorney, Agent, or Firm-Richard S. Sciascia', Ervin [22] Filed: June 4, 1973 F Johnston 21 Appl. NO.I 366,940

[57] ABSTRACT [52] US. Cl 2 114/16 E A compensator for an underwater deep submergence [51] hit. Cl. H 863G 8/00 fl System wherein the compensator includes a y [58] held of Search 114/16 [6 235 B; der and piston combination; one end of the cylinder 138/26 31; 61/69 69 A being connected to the fluid system and the other end thereof opening to the ambient water environment; [561 References cued and the cylinder being pre-pressurized to a predeter- UNITED STATES PATENTS mined pressure so that the system components can be 3,112,724 12/1963 Rosen 114/16 E f minim m volume and construction. 3,375 8OU 4/1968 Cole et a1 1. 114/235 B 3,590,761 7/1971 Parkes 114/16 R 5 Clam, 3 Drawing Flgures ;gA/U'fm:- 10 f4 31%;: at; ALVE LVE 12 )2 7 50 F051, P546719? 7/ -Pfiassuzs (aw-5mm (be/ r 0) Z? DEEP SUBMERGENCE PRESSURE COMPENSATOR STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The present invention relates to a compensator for an underwater deep submergence fluid system wherein the fluid system and the compensator are optimized for minimum volume and construction to withstand the pressure at the operating depth.

Remotely controlled underwater work vehicles are now being built for deep submergence work at the 20,000 ft. level within the ocean. These vehicles, like most underwater vehicles, require a means for changing the buoyancy so as to negotiate the descent and as' cent evolutions as desired. One of the best means for accomplishing the change in buoyancy has been the use of liquid hydrazine which is reacted in a reactor to produce large volumes of gas for deballasting a buoyancy tank. Accordingly, when it is desired to ascend the hydrazine is released to produce reacted gas for deballasting the buoyancy tank, and when it is desired to descend water is allowed to enter and ballast the buoyancy tank.

It is essential that the system components in contact with the hydrazine be kept dry since water penetration into the reactor will destroy the effect of the catalytic action on the hydrazine. It should be noted that water sealing the fluid system is a difficult task because of the high compressibility of the gas and the deep submergence operation at 20,000 feet. In a descent to 20,000 feet the volume of the gas mixture is reduced by a factor of approximately 600. Accordingly, the challenge is to provide a fluid system which is optimized in size and construction so that it is not too bulky or heavy.

Several proposals have been made to provide a fluid pressure compensating system which would be pressure sealed at deep submergence depths. These proposals are as follows: (1) construct the system completely of pressure components so as to withstand the high pressures; (2) compensate the system with an accumulator; and (3) compensate the system with system generated gas.

The first proposal, which is uncompensated, requires very heavy components to withstand the full operating pressure. This approach unduly weights the system and also subjects various valves to extremely high pressures.

The second proposal would utilize an accumulator to pressure compensate the system. Unfortunately, the accumulator would have to be quite large to accommodate the gas volume change from the surface to 20,000 feet in depth. For instance, to compensate a system volume of one cubic foot from the surface to 20,000 feet an accumulator would be required to have a volume of approximately 600 cubic feet. Here again, the accumulator would be unduly large and the added weight would be a burden.

The third proposal bleeds a small amount of hydrazine to the reactor for providing reacted pressurized gas to maintain a compensation level as the vehicle descends. The amount of hydrazine bled to the reactor would be controlled by a depth sensor which is coupled to an electrical feedback switching control circuit. The problem with this proposal is the complexity and reliability of the control system.

SUMMARY OF THE INVENTION The present invention has overcome the problems associated with the aforementioned proposals by providing a fluid pressure compensating system which is optimized in volume and strength. In the present invention the fluid pressurizing system has a pressure compensator which includes a piston and a cylinder combination. The system is pre-pressurized at a value which is approximately one third of the intended operating pressure of the system. The volume of the cylinder is approximately equal to the volume of the remainder of the system, and the entire system including the cylinder is capable of withstanding an interior and an exterior pressure equal to approximately the pre-pressurized value. In this manner, the system is subjected to an interior pressure equal to the prepressurized value at the surface. This interior pressure is reduced to zero when the volume of the system is at about one third the operating depth, the compensator operates between the one third to two thirds of the operating depth to pressure balance the system during this descent phase, and the entire system is then subjected to a gradually increasing exterior pressure which equals the pre-pressurized value when the system has reached the operating depth level. Optionally, the compensator can be constructed a little larger so that after the system has reached the depth which is equal to the pre-pressurized amount the depth compensator will compensate for the remainder of the descent to the operating level. In this optional embodiment the system is fully pressure compensated at the operating depth.

OBJECTS OF THE INVENTION An object of the present invention is to provide an underwater deep submergence fluid system which is optimized in volume and strength.

Another object is to provide a compensator for an underwater deep submergence fluid system wherein the system and the compensator can be constructed of minimum wall thickness and the compensator can be made with a minimum volume.

Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention, when considered in conjunction with the accompanying drawings wherein:

DESCRIPTION OF THE DRAWINGS FIGS. 1 through 4 are schematic illustrations of one embodiment of the present invention at various stages of depth operation.

FIGS. 5 through 8 are schematic illustrations of another embodiment of the present invention at various stages of depth operation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views there is illustrated in FIGS. 1 through 4 a fluid system 10 which is optimized for volume and strength. This system includes a main fluid line 12 for receiving fuel, such as liquid hydrazine at one end, and

supplying gas at the other end to a buoyancy tank (not shown). Such a buoyancy tank is illustrated in US. Pat. No. 3,7 l6,009 and is utilized for raising and lowering an underwater vehicle. The hydrazine fuel may be supplied from a pressure tank (not shown) which is selectively controlled for releasing hydrazine into the main fuel line 12.

A reactor 14 may be connected within the main fuel line 12 for reacting the hydrazine fuel with a catalyst bed, thereby producing gas for deballasting the buoyancy tank.

A secondary fluid line I6 connects the main fluid line 12 to the ambient pressure environment. Within the secondary fluid line 16 there is connected to a pressure compensator 18 which includes a cylinder 20 and a piston 22. The piston 22 may be mounted for free floating action within the cylinder 20 without any piston rod.

Connected into the system, such as into the secondary line 16, there may be a valve and fitting 24 which may be utilized for prepressurizing the fluid system with an inert fluid which is compatible with hydrazine, such as nitrogen or helium. In the preferred embodiment the entire system 10 including the cylinder is pre-pressurized at a value P, which is approximately one-third the intended operating pressure P,, of the system. The volume of the cylinder V,- is made approximately equal to the volume of the remainder of the system V The entire system 10 including the cylinder 20 is constructed of such a strength to withstand first the interior pressure P and then an exterior pressure which is approximately equal to P,,.

A filter 26 may be inserted in the line 16 between the cylinder 20 and the outside ocean environment for filtering out any foreign particles as the sea water enters into the cylinder. A check valve 28 may be inserted in the main fluid line 12 upstream from the reactor 14 and downstream from the secondary fluid line 16 for allowing one way flow of fuel to the reactor, and a check valve 30 may be located downstream of the reactor for preventing any back pressure into the reactor from the buoyancy tank (not shown). Upstream from the check valve 28 and downstream from the check valve 30 there may be on and off valves 32 and 34 respectively at the ends of the main fluid line 12 for opening and closing the system as desired. Valves 32 and 34 may be solenoid valves so as to enable remote operation. With this arrangement the system volume 10 or V includes all of the volumes within the main fluid line between the on and off valves 32 and 34, the reactor 14, the secondary fluid line to the valve 24 and to the cylinder 20, and the cylinder 20 itself.

The sequence of operation of the embodiment 10 at various depths is illustrated in FIGS. I through 4. As shown in FIG. 4, the intended operating depth is 20,000 feet however, this will vary depending upon the needs and the type of vehicle utilized. The valves 32 and 34 are selectively opened for the introduction of the liquid hydrazine and the discharge of reacted gas respectively. At the surface of the water the system is pre-pressurized through valve 24 to the value I which is approximately one-third of the value of the intended operating pressure P,,. The pressure at the operating depth of 20,000 is approximately 9,000 pounds per square inch. Accordingly, the system is pre-pressurized to a value of 3,000 pounds per square inch at zero depth causing the piston 22 to be bottomed out at the ambient end of the cylinder 20 with a force of 3,000

pounds per square inch acting thereon. As illustrated in FIG. 2, when the system has descended to a depth of 6,667 feet the system is pressure balanced and the forces acting on both sides of the piston 22 are the same. As the system descends from 6,667 feet to 13,600 feet the piston 22 progressively travels from the ambient end of the cylinder 20 to the opposite end, at which depth the system is still pressure balanced. During this phase (6,667 feet to l3,334 feet) the gas within the compensator I8 is used up for pressure balancing the remainder of the fluid system. As illustrated in FIG. 4, when the system descends from l3,334 to 20,000 feet the piston 22 remains in the same position and the ambient water environment now exerts an exterior pressure on the system which is equal to P,,, namely 3,000 pounds per square inch.

It is now readily apparent that the fluid system in the embodiment 10 in FIGS. 1 through 4 has been optimized for volume and strength. The system components are constructed of sufficient wall thickness to withstand initial and final pressures while the compensator 20 is constructed for a minimum volume to take care of pressure compensation intermediate these pressure phases.

Another embodiment 40 of the fluid pressure system is illustrated in FIGS. 5 through 8. This system may be constructed identical to the system 10 illustrated in FIGS. I through 4 with the exception that the cylinder 42 will normally have a larger volume so that the system is not subjected to an exterior pressure at the operating depth. In this embodiment the cylinder 42 is prepressurized at a value P between ambient pressure at the surface and operating pressure P of the of the system at operating depth. The volume V of the cylinder 42 is then as follows:

where V equals the volume of the system exclusive of the volume of the cylinder 42. It is preferable that the system 40 be pre-pressurized to one-third of the pressure at the intended operating depth. Assuming that the operating depth is 20,000 feet the pre-pressurization would be 3,000 pounds per square inch. As illustrated in FIG. 5, the piston 22 would be bottomed out under a pressure of 3,000 pounds per square inch when the system is at zero depth.

As illustrated in FIG. 6, when the system has descended to 6,667 feet the system will be pressure balanced and the compensator will be ready for operation. As illustrated in FIG. 7 the piston 22 has moved halfway within the cylinder 42 to pressure compensate for the system, and as illustrated in FIG. 8 the system has just bottomed out at 20,000 feet, at which depth the system is still pressure compensated.

The advantage of the second embodiment over the first embodiment is that at the operating depth there is no external pressure and therefore no chance of com tamination of the system by sea water. Further, there is no pressure surge due to external pressure when the valve 32 is opened at its operating depth. However, the first embodiment has an advantage over the second embodiment in that the volume of the compensator is smaller.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. An underwater fluid system comprising:

a main fluid line for receiving fuel at one end and supplying gas at the other end;

a shut-off valve connected to the main fluid line at each respective end;

a reactor connected within the main fluid line for reto acting the fuel with a catalyst and producing the gas;

a secondary fluid line connecting the main fluid line to the ambient pressure environment;

a pressure compensator connected in the second fluid line;

the volume of the system V, being equal to the volumes of the of the main fluid line between the shutoff valves, the reactor, the pressure compensator, and the secondary fluid line to the pressure compensator;

said pressure compensator including a piston and cylinder combination;

said cylinder and the remainder of the system containing a fluid which is pre-pressurized at a value P above ambient pressure which is approximately one third the intended operating pressure P of the system;

the volume of the cylinder V being approximately equal to the volume of the remainder of the system V and the entire system including the cylinder having a structural strength which is capable of withstanding first the interior pressure P,, and then an exterior pressure equal to approximately P,,.

2. An underwater fluid system as claimed in claim 1 including:

said piston being mounted for free floating reciprocation within the cylinder; and

said piston reciprocating to the opposite end of the cylinder when the system is at approximately two thirds of its operating depth.

3. An underwater fluid system as claimed in claim 2 5 including:

a valve and fitting connected to the system for prepressurizing the system.

4. An underwater fluid system comprising:

a main fluid line for receiving fuel at one end and supplying gas at the other end;

a shutoff valve connected to the main fluid line at each respective end;

a reactor connected within the main fluid line for reacting the fuel with a catalyst bed and producing the gas;

a secondary fluid line connecting the main fluid line to the ambient pressure environment;

a pressure compensator connected in the second fluid line;

the volume of the system V, being equal to the volumes of the main fluid line between the shut-off valves, the reactor, the pressure compensator, and the secondary fluid line to the pressure compensator;

said pressure compensator including a piston and cylinder combination;

said cylinder and the remainder of the system being prepressurized at a value P,, between ambient pressure at the surface of the water and operating pressure P of the system at operating depth;

the volume of the cylinder V being as follows:

where V equals the volume of the system exclusive of the cylinder volume. 5. An underwater fluid system as claimed in claim 4 said piston bottoming out at the ambient end of the wherein: P, equals approximately one third P,,.

cylinder when the system is pre-pressurized and 

1. An underwater fluid system comprising: a main fluid line for receiving fuel at one end and supplying gas at the other end; a shut-off valve connected to the main fluid line at each respective end; a reactor connected within the main fluid line for reacting the fuel with a catalyst and producing the gas; a secondary fluid line connecting the main fluid line to the ambient pressure environment; a pressure compensator connected in the second fluid line; the volume of the system Vs being equal to the volumes of the of the main fluid line between the shut-off valves, the reactor, the pressure compensator, and the secondary fluid line to the pressure compensator; said pressure compensator including a piston and cylinder combination; said cylinder and the remainder of the system containing a fluid which is pre-pressurized at a value Pp above ambient pressure which is approximately one third the intended operating pressure Po of the system; the volume of the cylinder Vc being approximately equal to the volume of the remainder of the system Vrs; and the entire system including the cylinder having a structural strength which is capable of withstanding first the interior pressure Pp and then an exterior pressure equal to approximately Pp.
 2. An underwater fluid system as claimed in claim 1 including: said piston being mounted for free floating reciprocation within the cylinder; and said piston bottoming out at the ambient end of the cylinder when the system is pre-pressurized and said piston reciprocating to the opposite end of the cylinder when the system is at approximately two thirds of its operating depth.
 3. An underwater fluid system as claimed in claim 2 including: a valve and fitting connected to the system for pre-pressurizing the system.
 4. An underwater fluid system comprising: a main fluid line for receiving fuel at one end and supplying gas at the other end; a shut-off valve connected to the main fluid line at each respective end; a reactor connected within the main fluid line for reacting the fuel with a catalyst bed and producing the gas; a secondary fluid line connecting the main fluid line to the ambient pressure environment; a pressure compensator connected in the second fluid line; the volume of the system Vs being equal to the volumes of the main fluid line between the shut-off valves, the reactor, the pressure compensator, and the secondary fluid line to the pressure compensator; said pressure compensator including a piston and cylinder combination; said cylinder and the remainder of the system being prepressurized at a value Pp between ambient pressure at the surface of the water and operating pressure Po of the system at operating depth; the volume of the cylinder Vc being as follows:
 5. An underwater fluid system as claimed in claim 4 wherein: Pp equals approximately one third Po. 